This invention relates generally to a crane system, and more particularly, to a rotating, radiation shielded crane system.
For the next phase of the United States Fusion Program, a compact high-field, toroidal ignition machine, designated the Compact Ignition Tokomak (CIT) is proposed. The CIT machine will be housed in a test cell which must be designed to provide shielding from the ionizing radiation resulting from the CIT full power pulses. The CIT will be fueled by Deuterium-Tritium (D-T). During operation, it will generate high-energy neutrons and may release tritium to the test cell atmosphere. After tritium operation begins, the machine will quickly become activated to a radiation level that will prevent personnel access to the test cell. Maintenance requirements necessitate a crane system which has access to the CIT machine and its ancilliary equipment.
Conventional tests cell/crane designs include a crane system which is housed in the test cell itself. A crane system having maximum reach capabilities, as the one disclosed in U.S. Pat. No. 3,770,137 may be used in this design.
Such a design, however, has several disadvantages. The test cell must have a larger overhead capacity to accommodate the crane system. Neutron activation of the crane will complicate maintenance procedures for the crane itself. If the crane becomes activated, the crane must be transferred to either a hot cell or a warm cell for maintenance. The warm cell is used only if hands-on work can be performed under controlled conditions; the hot cell is used for completely remote work. To prevent activation of the crane, it must be positioned away from the CIT machine during machine operation, thereby requiring a larger floor space for the test cell. Further, the crane must be positioned at a distance sufficient to insure that the magnetic materials in the crane will not interfere with the CIT field magnets.
From an economic viewpoint, there will be larger construction costs associated with a larger test cell. Since there will be no radiation shielding close to the machine, the air in the test cell will become activated during a pulse. A larger test cell means that a larger volume of the test cell itself is subject to tritium contamination and that a larger volume of air will be subject to activation. The activated air must be held in a radiation-shielded holdup vessel for a sufficient time to assure that the activation is reduced to a safe level for release to the atmosphere. Nitrogen-13, a positron emitter with a half-life of 10 minutes, will be at a level of about 2.times.10.sup.6 pCi/cc (too high for release directly to the environment). Holding up the air for nine half-lives of nitrogen-13 (90 min.) will reduce the activation to a safe level for release. The most direct method for holdup of test cell air is to use the test cell itself as the radiation-shielded holdup vessel. Therefore, for safety reasons, the test cell design must also provide seals against leaks of tritium and activated air from the test cell.
Therefore, in view of the above, it is an object of the present invention to provide a crane system for use in high radiation test environment which will be shielded from radiation and tritium exposure.
It is a further object of the present invention to provide a shielded crane system which has maximized reach capabilities inside the test cell.
It is a further object of the present invention to provide a crane system which will minimize the amount of electromagnetic interference between the CIT machine and the crane.
It is a further object of the present invention to provide a test cell crane system which will minimize the volume of test cell subject to tritium contamination and minimize the volume of air subject to activation.
It is still a further object of the present invention to provide a test cell crane shield system which will provide for tritium and activated air containment.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.